The invention concerns a method for treating an air flow to be sent into the passenger compartment of a vehicle, in which the air flow, before being exposed where necessary to a heat source, passes through an evaporator which forms part of a refrigerating fluid circuit also comprising a compressor, a condenser and at least one pressure reducing valve, taking account of the choice made by a user between at least one working mode of the said circuit in which the fluid circulates in the evaporator so as to modify the temperature of the air flow and an idle mode in which the fluid does not circulate in the evaporator.
Such a method is commonly used for air conditioning the vehicle passenger compartment. It is also used, by means of a refrigerating fluid circuit like those described in FR-A-2 717 126 and FR-A-2 731 952, in a working mode where the evaporator yields heat to the air flow, in order to supplement an insufficient contribution by the heat source, in particular when the latter is a heat exchanger through which the fluid cooling the engine driving the vehicle passes, and the engine, and consequently the cooling fluid, have not reached their normal operating temperature.
It is also known that the appearance of mist on the windows can be detected by means of a suitable sensor, and that the sensor signal can be used for triggering an action aimed at eliminating the mist. This action consists of favouring the sending of hot air to the misted glazed surfaces, either by modifying the distribution of the treated air flow between different outlet vents in the passenger compartment, or by an overall increase in the rate of this flow, or by increasing the exchanges between the latter and the heat source, or by combining these different methods. In no case does the signal from the mist sensor act on the circulation of the refrigerating fluid.